Photo credits

Photos from Wikimedia Commons, used under the licences shown. Thanks to their authors.

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  The Colosseum seen from outside on a sunny day, with its three tiers of arches against a blue sky

  Christoph Strässler · CC BY-SA 2.0 · colours and contrast edited

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  The outer wall of the Colosseum on the east side, with the brick buttress, under a blue sky

  Dietmar Rabich · CC BY-SA 4.0 · colours and contrast edited

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  Inside the Colosseum: the tiers of seating, the arena and the exposed corridors below its floor

  Suicasmo · CC BY-SA 4.0 · colours and contrast edited

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  The arena of the Colosseum with the rebuilt floor and the tiers of seating around it

  Colin · CC BY-SA 3.0 · colours and contrast edited

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  The hypogeum of the Colosseum: brick walls and corridors under the arena floor

  daryl_mitchell · CC BY-SA 2.0 · colours and contrast edited

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  The Colosseum and the Arch of Constantine seen from the Palatine Hill

  Livioandronico2013 · CC BY-SA 4.0 · colours and contrast edited

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  The Arch of Constantine, with its three openings and carved reliefs

  Joseolgon · CC BY 4.0 · colours and contrast edited

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  The Colosseum and the Arch of Constantine under a clear blue sky

  Anil Öztas · CC BY 4.0 · colours and contrast edited

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  The Colosseum at dusk, with its arches lit from inside and a pale evening sky behind

  Wilfredor · CC0 · colours and contrast edited

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  The Colosseum in the distance, behind the Arch of Titus and the umbrella pines

  Radek Kucharski from Warsaw, Poland · CC BY 2.0 · colours and contrast edited

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  The Colosseum at dawn under a streaked blue and violet sky, with the road and the square in front

  Thomas_Fuhrmann_Jakobsthal · CC BY-SA 4.0 · colours and contrast edited

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  The Colosseum's outer arcades seen from Piazza del Colosseo, with the street sign for the square

  Silar · CC BY-SA 4.0 · colours and contrast edited

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  Panorama of the Roman Forum with the Arch of Septimius Severus and rows of ancient columns

  Nicholas Hartmann · CC BY-SA 4.0 · colours and contrast edited

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  The Tabularium and the Palazzo Senatorio above the Roman Forum, with the Arch of Septimius Severus on the right

  Gary Todd · Public domain · colours and contrast edited

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  The Arch of Titus, a single-arched triumphal arch at the top of the Via Sacra

  Tournasol7 · CC BY-SA 4.0 · colours and contrast edited

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  The Column of Phocas, the Arch of Septimius Severus and the Curia in the Roman Forum, under a blue sky

  Sonse · CC BY 2.0 · colours and contrast edited

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  The columns of the Temple of Saturn in the Roman Forum

  Joseolgon · CC BY 4.0 · colours and contrast edited

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  The ruins of the House of the Vestals in the Roman Forum, with its garden

  Sjaak Kempe · CC BY 2.0 · colours and contrast edited

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  The Stadium on the Palatine Hill, a long open space surrounded by ruins

  Daderot · CC0 · colours and contrast edited

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  The Farnese Gardens on the Palatine Hill, with the Aviaries

  JTSH26 · CC BY-SA 4.0 · colours and contrast edited

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  The Circus Maximus seen from the Palatine Hill

  Livioandronico2013 · CC BY-SA 4.0 · colours and contrast edited

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  The façade of St Peter's Basilica in Vatican City

  Livioandronico2013 · CC BY-SA 4.0 · colours and contrast edited

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  Castel Sant'Angelo, the round fortress on the Tiber

  Livioandronico2013 · CC BY-SA 4.0 · colours and contrast edited

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  Piazza del Campidoglio on the Capitoline Hill, with its palaces and the paved square

  Nhartmannphotos · CC BY-SA 4.0 · colours and contrast edited

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  Via dei Fori Imperiali, the avenue lined with umbrella pines that runs past the Imperial Forums

  Sonse · CC BY 2.0 · colours and contrast edited

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  The façade of the Galleria Borghese in the gardens of Villa Borghese, under a blue sky

  Alessio Damato · CC BY-SA 3.0 · colours and contrast edited